Buy dried beans, peas,lentils etc. soak them overnight and make them into a soup or chili. I soak a cup of dried beans for the next day's soup, a few times a week. Pasta is nice with sauteed veggies of any sort over them. Chicken is cheap, hold down the meat, you can go vegetarian. Oatmeal for any meal is good and quick. Bake your own bread, it's therapeutic, I bake 2 loaves of sourdough bread twice a week.
Rice is cheap and like pasta blends well with a layer of veggies on it. Buy the vegetables either in season or frozen. Fruit is my dessert, if i have some. it's easy to feed yourself cheaply and better for you.